﻿(function () {
    /** 
     * From: http://code.this.com/mobile/articles/fast_buttons.html
     * Also see: http://stackoverflow.com/questions/6300136/trying-to-implement-googles-fast-button 
     */

    /** For IE8 and earlier compatibility: https://developer.mozilla.org/en/DOM/element.addEventListener */
    function addListener(el, type, listener, useCapture) {
        if (el.addEventListener) {
            el.addEventListener(type, listener, useCapture);
            return {
                destroy: function () { el.removeEventListener(type, listener, useCapture); }
            };
        } else {
            // see: http://stackoverflow.com/questions/5198845/javascript-this-losing-context-in-ie
            var handler = function (e) { listener.handleEvent(window.event, listener); }
            el.attachEvent('on' + type, handler);

            return {
                destroy: function () { el.detachEvent('on' + type, handler); }
            };
        }
    }

    var isTouch = "ontouchstart" in window;

    /* Construct the FastButton with a reference to the element and click handler. */
    this.FastButton = function (element, handler, useCapture) {
        // collect functions to call to cleanup events 
        this.events = [];
        this.touchEvents = [];
        this.element = element;
        this.handler = handler;
        this.useCapture = useCapture;
        if (isTouch)
            this.events.push(addListener(element, 'touchstart', this, this.useCapture));
        this.events.push(addListener(element, 'click', this, this.useCapture));
    };

    /* Remove event handling when no longer needed for this button */
    this.FastButton.prototype.destroy = function () {
        if (this.events) {
            for (i = this.events.length - 1; i >= 0; i -= 1)
                this.events[i].destroy();
            this.events = this.touchEvents = this.element = this.handler = this.fastButton = null;
        }
    };

    /* acts as an event dispatcher */
    this.FastButton.prototype.handleEvent = function (event) {
        switch (event.type) {
            case 'touchstart': this.onTouchStart(event); break;
            case 'touchmove': this.onTouchMove(event); break;
            case 'touchend': this.onClick(event); break;
            case 'click': this.onClick(event); break;
        }
    };

    /* Save a reference to the touchstart coordinate and start listening to touchmove and
     touchend events. Calling stopPropagation guarantees that other behaviors don’t get a
     chance to handle the same click event. This is executed at the beginning of touch. */
    this.FastButton.prototype.onTouchStart = function (event) {
        event.stopPropagation ? event.stopPropagation() : (event.cancelBubble = true);
        this.touchEvents.push(addListener(this.element, 'touchend', this, this.useCapture));
        this.touchEvents.push(addListener(document.body, 'touchmove', this, this.useCapture));
        this.startX = event.touches[0].clientX;
        this.startY = event.touches[0].clientY;
    };

    /* When /if touchmove event is invoked, check if the user has dragged past the threshold of 10px. */
    this.FastButton.prototype.onTouchMove = function (event) {
        if (Math.abs(event.touches[0].clientX - this.startX) > 10 || Math.abs(event.touches[0].clientY - this.startY) > 10) {
            this.reset(); //if he did, then cancel the touch event
        }
    };

    /* Invoke the actual click handler and prevent ghost clicks if this was a touchend event. */
    this.FastButton.prototype.onClick = function (event) {
        event.stopPropagation ? event.stopPropagation() : (event.cancelBubble = true);
        this.reset();
        // Use .call to call the method so that we have the correct "this": https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Function/call
        var result = this.handler.call(this.element, event);
        if (event.type == 'touchend')
            clickbuster.preventGhostClick(this.startX, this.startY);
        return result;
    };

    this.FastButton.prototype.reset = function () {
        for (i = this.touchEvents.length - 1; i >= 0; i -= 1)
            this.touchEvents[i].destroy();
        this.touchEvents = [];
    };

    this.clickbuster = function () { }

    /* Call preventGhostClick to bust all click events that happen within 25px of
     the provided x, y coordinates in the next 2.5s. */
    this.clickbuster.preventGhostClick = function (x, y) {
        clickbuster.coordinates.push(x, y);
        window.setTimeout(clickbuster.pop, 2500);
    };

    this.clickbuster.pop = function () {
        clickbuster.coordinates.splice(0, 2);
    };

    /* If we catch a click event inside the given radius and time threshold then we call
     stopPropagation and preventDefault. Calling preventDefault will stop links
     from being activated. */
    this.clickbuster.onClick = function (event) {
        for (var i = 0; i < clickbuster.coordinates.length; i += 2) {
            var x = clickbuster.coordinates[i];
            var y = clickbuster.coordinates[i + 1];
            if (Math.abs(event.clientX - x) < 25 && Math.abs(event.clientY - y) < 25) {
                event.stopPropagation ? event.stopPropagation() : (event.cancelBubble = true);
                event.preventDefault ? event.preventDefault() : (event.returnValue = false);
            }
        }
    };

    if (isTouch) {
        // Don't need to use our custom addListener function since we only bust clicks on touch devices
        document.addEventListener('click', clickbuster.onClick, true);
        clickbuster.coordinates = [];
    }
})(this);